10 Fun Facts About Jupiter | The Old Farmer's Almanac

10 Fun Facts About Jupiter, the Giant Planet

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Jupiter’s auroras arise from a magnetic ‘tug-of-war’ with volcanic eruptions on its innermost moon, Io!

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NASA/ESA/J. Nichols
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Plus interesting facts about Jupiter's moons

Bob Berman
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Jupiter, the king of all planets is named after the king of gods in Roman mythology! How many moons does Jupiter actually have? Is the red spot permanent? Does Jupiter protect Earth? Find fun facts about Jupiter, including recent discoveries from the Juno spacecraft mission.

Jupiter Fun Facts

  1. The biggest planet in our solar system, Jupiter was named after the god of sky and thunder. Jupiter is SO massive that you could put all of the other planets inside—twice over! Elevent Earths could fit across the Giant Planet. But what’s interesting is that this star-sized planet is almost all gas (hydrogen and helium) so it’s inner core is close to the size of Earth.
  2. Jupiter reigns over a miniature solar system of at least 79 moons, including huge and ever-changing Io, Europa, Ganymede, and Callisto (named the Galilean Satellites in Galileo’s honor).  While Jupiter cannot support life, some of its moons might be able to do so, given the oceans beneath the surface.
  3. Its rotation is faster than that of any other planet, which creates streaks: dark areas (belts) indicate rising clouds and gases; light areas (zones) indicate where belts sink. 
  4. It spins fast at its equator and slowly at its poles; where the momentums clash, gaseous layers produce violent eddies, curlicues, swirls, white spots, and the famous Great Red Spot—a hurricane three times the size of Earth that’s not permanent but has been ranging for over a century! (You can see this on nights when Earth’s air is steady.) 
  5. Jupiter has four rings! They were discovered by the Voyager 1 spacecraft in 1979. They are very faint and made of small dust particles unlike Saturn’s visible rings which are made of large icy and rock chunks.

Image (from top to bottom): Jupiter’s Great Red Spot, Io, Europa, Ganymede, Callisto. NASA.

Does Jupiter Protect Earth?

Readers often ask about Jupiter’s role in our lives. Does Jupiter protect Earth? Yes and no. It’s massive size and gravity can affect the paths of comets and asteroids. And it’s fairly clear that comets have hit Jupiter, which most probably protected our planet. At the same time, Jupiter has the power to divert asteroids into a new orbit and, accidentally or not, direct them on a path to collide with Earth.

 Image: Juno captured the hurricane-like spiral wind patterns – near the planet’s north pole. ASA/JPL-Caltech/SwRI/MSSS.

5 New Facts From the Juno Mission

Right now, NASA spacecraft “Juno”  is orbiting Jupiter! Juno was launched in 2011, arriving at Jupiter in 2016. It was a 1,740-million-mile journey from Earth to Jupiter which took five years, and the Juno spacecraft will explore until 2025 or the end of its life.

The Juno spacecraft is the first spacecraft to go below the dense clouds of the planet. Interesting, Juno is named after the goddess Juno, who was Jupiter’s wife in Roman mythology. According to mythology, Jupiter liked to hid beneath the clouds but Juno had the ability to peer through them. 

What have we learned so far? The results are Earth-shattering (ahem, Jupiter-shattering) and worth the long journey.

  1. Jupiter’s atmosphere was a surprise. The gas giant has a much more turbulent world than imagined. The clouds and windy weather aren’t just at the top layer. Rather, the winds churn thousands of kilometers beneath. Another surprise was that Jupiter’s signature bands disappear near its poles.
  2. In addition, we assumed that Jupiter’s famous gas clouds (made of a mix of water and ammonia) were evenly mixed. However, there is less ammonia on the surface level and more ammonia near the core. What results are ammonia-heavy hail storms called ”mushballs” plunging to the depths within the planet.
  3. At Jupiter’s north and south poles circle chains of continent-sized cyclones! These powerful Earth-sized swirling storms are densely clustered and rubbing together, up to 30 miles in height and hundreds of miles across. Interesting, they seem to stay put at the poles for a never-ending polar cyclone party.
  4. The planet’s solid core at the center is not compact! It’s a bloated, fuzzy sphere that’s nearly half of Jupiter’s diameter! No one knows why, but it’s hypothesized that Jupiter might have been hit by a massive object which mixed up its material core with the surrounding gases.
  5. Jupiter has the strongest magnetic field in the Solar System, but Juno revealed that it’s even stronger than expected and closer to the planet’s surface than previously thought. Also, Jupiter’s north and south poles aren’t similar. The northern end isn’t defined but more diluted across the northern tiers, while the southern end is more centralized like Earth’s pole. 

Juno recently flew by Ganymede, Jupiter’s monster-sized moon (26% bigger than the planet Mercury!) and will fly by the icy Moon Europe on September 29, 2022. More learning to come about Giant Jupiter and its moons!

Image: Ganymede.  NASA/JPL.

Jupiter by the Numbers

  • Diameter: 11 Earths
  • Mass (quantity of matter): 318 Earths
  • Volume: 1,312 Earths
  • Length of year: 11.86 Earth years
  • Length of day: 9 hours 56 minutes
  • Surface temperature: –234°F
  • Density: 1⁄4 of Earth’s
  • Gravity: 2.4 times stronger than on Earth (a
  • 100-lb. person would weigh 240 lbs. on Jupiter)
  • Magnetic force: 14 times stronger than Earth’s
  • Average distance from the Sun: More than 5 times Earth’s
  • Closest distance to Earth: 367 million miles
  • Brightness, on average: Magnitude –2.3
  • Natural satellites (moons): At least 79